Magnetic chuck



Jne 16, 1942. F. l.. SIMMONS MAGNETIC CHUCK 6. Sheets-Sheet l Filed Dec.l0, 41938.

June 16, 1942. F. L.. SIMMONS y 2,286,238

MAGNETIC CHUCK Filed Dec, l0,` 1938 6 Sheets-Sheet 2 44 29x55 3% 32 4 232 ZZ lull* l' A 16. a 29 29 22 29 zg 32 ZIZ l 2,2 Il /\,/.,2 210 wwwSummer Fan/4 L. cf'wzmona' June'ls, 1942. F L SIMMONS 2,286,238

' MAGNETIC CHUCK Filed Dec. l0, 1938 6 Sheets-Sheet 3 Summer June 16,1942. F L SMMONS 2,286,238

MAGNETIC CHUCK Filed Deo. 1o, 1958 e sheets-sheet 4 w @66 6; I I3 gi/5.

// EWS/ i a 92 92 W W3 v F. L.. SIMMONS MAGNETIC CHUCK June 16, 1942.

6 Sheets-Sheet 5 Filed Deo.

54 2v 0 2,., 2 ma.. m f, M 1w.. .d 0 j -m 6 Sheets-Sheet 6 MAGNETI CCHUCK JH 276 J72 J7.9

F. L.. SIMMONS Filed Dc. 1o, 1958 June 16, 1942.

WMV/z (ltarrug Patented June 16, 1942 UNITED' STATES PATENT' OFFICE '11Claims.

My invention relates to magnetic chucks, and

l more particularly to a chuck employing a permanent magnet therein.

The recent improvement in permanent magnets has suggested thesubstitution' thereof for the standard electromagnets heretofore used inchucks. It, however, is possible to releasethe work readily and quicklyfrom an electromagnet by reversing the current and neutralizing the polepieces supporting the Work. But, a'permanent magnet tends to hold theIwork fixed in position and requires a strong force for removing thework therefrom. It has been proposed to overcome this difficulty byproviding a shunt circuit for the magnetic fiux when it is required toremove the work from the chuck. Such a construction has comprised a setof narrow horseshoe magnets so arranged relatively to a pole piece platewhich supports the work that the magnets may be moved bodily to aposition where the pole piece forms a shunt circuit for part of the fluxand thus decreases the holding force of the chuck. Since part of thelines of force still pass through the work, this requires the use offorce for removing the work; and if the undersurface of the work hasbeen finely polished, there is danger of scratching or marrng it. Tobuild such a construction, the narrow magnetsmust be first ground tosize and assembled on brass rods with brass spacers and fitted intoplace in the chuck, then removed for heat treatment and to bemagnetized. and thereafter reassembled, with the .possibility of poorworkmanship making an inferior construction, The new alloy, sold underthe trade name of Alnico, which is now employed for permanent magnets,is extremely hard and cannot be readily machined but must be cast insubstantially the desired shape and then have its surfaces ground to therequired finish. This makes the use of smallv magnets a serious expense.If, to save expense, the faces of the magnet are left rough, they do notmake proper contact with the` other members forming the magnetic circuitand thus cause a loss of power; andY it is more difficult to secure themrigidly together, as is necessary to make a strong chuck for holdingheavy pieces of work against the pull of 'a grinding or a machinedoperation. It moreover has been proposed, in order to get the maximumholding power in such constructions, that two` such disadvantages and toprovide a construction which gives a strong and uniform field capableofA holding both large and small objects securely in place.

A further object is to provide a chuck having a permanent magnet whichis so constructed that a work piece may be readily removed therefrom.

In accordance with my invention, I propose to use in a chuck a singlelarge sized permanent magnet, or a plurality assembled together, and toprovidev a return path for the lines of force from the magnet througheither the framework of the chuck or an adjacent magnet of oppositelyarranged polarity. I also propose to neutralize the pole pieces of thechuck, so that the work may be readily removed therefrom, by temporarilyisolating one pole of the magnet from the other, and particularly bybreaking the magnetic circuit between both poles of the magnet orbetween one or both poles of the magnet andthe associated pole piecesandthe work held thereby, This is preferably accomplished by soarranging and shaping the magnet 'and associated pole pieces that onemay be moved relatively to the other to position the parts in eitheroperative or inoperative positions; and power mechanism may be providedfor the purpose. 'A small chuck may'comprise one large bar magnetarranged to magnetize spaced pole pieces of one polarity and framepieces of the-opposite polarity. A larger chuck may be formed ofsubstantially a duplication of that construction. Also, -Imay make achuck of three, or multiples of three, large bar magnets arranged withalternate north and south poles uppermost and so constructed as to givea satisfactory distribution of the lines of force at the work surfaceand to provide for breaking the circuit, as required.- i

It is accordingly a further object of my invention to make a magneticchuck one or more massive bar magnets therein constructed and arrangedto give a strong field which is so distributed as to hold small or largework pieces .firmly thereon.

Another object is to provide chucks of the types herein described whichpermit easy removal of the work pieces without injury thereto -and whichmay be readily operated to magnetize or to da Fig. 1 is a plan view,partlyv broken away, of

' one form o f chuck having two` permanent bar magnets therein;

Fig, 2 is a section on the line 2--2 of Fig. 1; Fg..3 'is a perspectiveview of the two bar mag- Tnets of Fig. 1 in their assembledrelationship;

Fig. 4 is a section on the line` 4-4 of Fig. 1;

Fig. 5 is a section on the line 5-5 of Fig. 1;

Fig. 6 is a plan view ofthe bottom and sides of the chuck with the topwork plate, magnets and operating mechanism removed;

Fig. 7 is a view similar to Fig. 2, showing the parts in an inoperativeposition;

Fig. 8 is a top plan View of a modication showing a dilferent type ofwork carrying plate, part of the plate being broken away; y

Fig. 9 is a section on line 9-9 of Fig. 8, with the plates in theiroperative work holding positions;

Fig. 10 is a perspective view of the two assembled bar magnets of Fig.8; l

Fig. 11 is a section on the line I I-II of Fig. 9;

Fig. 12 is a section on the line I2-I2 of Figf9;

Fig. 13 as a view, partly in section, and partly in elevation,y with theparts in inoperative positions as contrasted with the view in Fig. 9;

Fig. 14 is a modification showing in a sectional view, partly inelevation, a diierent type of bar magnet and embodying a fluid pressuremechanism for moving the magnet;

Fig. 15 is a sectional detail on the line I5-I5 of Fig. 14 showing theiluid pressure and valve mechanism;

Fig. 16 is a top plan view of a further modication with the work platepartly broken away, which shows an arrangement embodying threebai-magnets; y

Fig. 17 is,` a section onthe line I1-I1 of Fig. 16; y l y' i Figs. 18and 19 are secti ns oni-the lines I8 and I9 of Fig. 16;

Fig. 20 isa fragmentary detail `corresponding with Fig. 17 with themagnet in ani inoperative position;v f

Fig. 21 is a view corespondingwith Fig. 2Q,

` showing a modied type of barmagnet;

Fig. 22 is a fragmentary top plan view of a modification of the workvplate of Fig. 16;

Fig. 23 is a section on the line 23-23 of Fig. 22;

` magnet so constructed and arranged that the which is sold under thetrade name of Alnicof As'illustrated in Fig. 3, the magnets are .shapedas massive solid bars and not as narrow spaced separate magnets, so thateach bar acts as a single magnet and the lines of force are distributedaccordingly. A narrow chuck may comprise but one bar magnet and acorresponding change in construction; but in the form shown I haveillustrated two permanent magnets I0 and I2 which have corrugatedsurfaces providingspaced lribs or polar pieces I4 and I6 terminating inyspaced polar faces at their top and bottom portions respectively, whichserve as the north and south poles. or vice versa, of the magnets. Asillustrated in Fig. 2,'the assembled magnets are slidably mountedbetween a base plate I8 and a top plate or frame 20 which may form thework support. The frame 20 may be made'of Swedish or wroughtiron whichdoes not retain residual magnetism; and it is` so constructed as toprovide openings for a set of spaced pole pieces 22 magneticallyisolated from the frame and suitably mounted in the frame. These polepieces are arranged to contact with or to be in magnetic circuit withthe upper spaced polar faces on the ribs of the permanent magnet, andthey may be considered as north poles. The lower spaced south polar-faces on the ribs I6 are in contact with spaced ribs 24 of the bottomplate I8, which may be made of low carbon steel. The sides 26 which reston plate I8 and support the top plateare also made of iron, steel orother suitable magnetic material. Hence, the lines of force may traversefrom the north pole of the magnet to the pole pieces 22 in the workplate, then through a work piece supported thereon, and thence back intothe top frame 20 and through the side walls 26 and the lower plate I8`oi' the chuck casing to the south pole of the permanent magnet.

The top plate is constructed as shown particularly in Fig. 1. Itcomprises'an iron plate or a welded structure-having two sets of spacedrectangular openings 28 therein separated by iron cross bars 29 and asingle longitudinal bar 30.'

, isolated magnetically from the cross bars 29 and magnetic iiux may bebroken between the two poles of the magnet and particularly between bothpoles of the magnet and the pole pieces which contact with the work. Themagnetic lines may be broken at one pole of the magnet forcertain typesof magnetic chucks, or they may be broken at both poles so as to isolatethe permanent magnet completely from the work which is supported by thechuck.

In the form shown in Figs. 1 to 7 inclusive, I have shown an arrangementin which one or more permanent magnets may be so arranged in the chuckthat the magnetic circuit may be broken at both thenorth and the southpoles thereof. These magnets may be constructed of suitable materialwell known in the industry, such as magnetizable high carbon steel or an30 o1' the frame. As shown particularly in Fig. 2, the non-magnetic.material 32 extends beneath the cross bars 29 and forms a surface whichlies I in substantially the same plane with the botalloy comprisingaluminum, nickel and cobalt toms of the inserts 22. 'Ihe bottom plate I8is similarly constructed to providespaced portions of magnetic andnon-magnetic material. That .is, the cut out spaces 38 between the ribs24 are nlled with brass, Babbitt metal or the like, and the dimensionsof these non-magnetic inserts 39 are such as to substantially preventthe passage of the ux therethrough. The top surfaces of the inserts 39lie in the same plane with the tops of the ribs, so that the magnet barmay slide thereover, and these surfaces are as wide as the width of thecut away space 36 in the magnet.

The parts are so constructed and located that when the magnet is intheposition of Fig. 2, the

azaaaaav ilux will pass to the pole pieces 22, then through a work pieceto the other set of pole pieces 29, thence through the sidewalls 26 tothe plate I8 and the bottom ribs of the magnet. If the permarient magnetis shifted laterally from the 4operative position of Fig. 2 to theinoperative position of Fig. '7, the north pole ribs I4 will be movedout of contact with the pole pieces 22 and lie beneath the non-magneticmaterial 32. Similarly, the lower pole ribs I6 will rest solely on thenonmagnetic inserts 39. Hence, the magnetic circuit is broken at bothpoles of the magnet. The north and south pole pieces in the top worksupporting plate are of substantially the same width, and the bottomsurfaces 34 of the-non-magnetic material 32 are much wider, as shown inFigs. 2

for holding small work pieecs in closely spacedv arrangement, because ofthe substantially equal holding areas of opposite polarities. The U-shaped portions 36 between the ribs I4 and I6 of the magnet are widerthan the pole pieces, and these spaces are cut deeply enough so as toprovide suillcient distance to prevent material leakage of flux from thepoles of the magnet. Four side plates of brass 40 fill the spacesbetween the inside walls of the two part chuck casing and themagnets andform the side walls of two troughs within which the magnets slide. Thetwo magnets may be connected together by a brass pin 42 or othersuitable non-magnetic material so that they may be moved together. Asshown in Fig. 4, an iron rib 44 is fitted in between the two innermostbrass plates 40, and it contacts with the longitudinal rib 30 on theunderside of the top plate 20 and thus forms a centrai partition whichserves as a part of the return circuit for the lines of force going fromsouth pole plate I8 to the set of pole pieces 29.

intervals around the edge of the casing and thereby making a rigidconstruction. 'I'his chuck will, of course, be suitably mounted on thework table of a machine tool, such as a grinding machine, as by means ofprojecting ears onA the chuck and T-bolts fastened to the work table.

The permanent magnets and the associated pole pieces or other suitablyrelated parts, such as the separate polar piece plate shownv in Fig. 26,may be moved relatively to each other to make or break the magneticcircuit, either manually or by a power operated mechanism. In theconstruction shown in Figs. 1 to '1, the magnets are arranged to bemoved by means of a manually operated mechanism, which comprises twospaced, axially aligned hubs 48 suitably mounted in bearing holes in theside walls '26' 'of the frame for rotation therein. A pin 50 connectsthe two hubs 'and is arranged eccentric with their axis. A handle 5I isconnected to one of the hubs so that rotationthereof serves to move thepin 50 through an arc. This pin 50 is slidably inserted into holes inthe two hubs and arranged for removal therefrom. The pin passes throughelongated slots 52 in the projecting ends of the T- shaped members 53,made of brass or other nonmagnetic material,;which are suitably' securedas by meansof brass rivets 54 to the permanent magnets. Af suitable hole55 (Fig. '7) is cut through the center plate 44 so as to permit propermovement of the eccentrically mounted pin 50. Hence, by suitablyrevolving the handle 5I, the permanent magnets may be moved from theoperative position of Fig. 2 to the inoperative position of Fig. 7. Whenin this latter position,

both the north and the south pole rib faces of the magnets arecompletely isolated from the spaced pole pieces22 and '29 in the workplate and the work may be readily removed from the chuck, since there isbut little residual magnetism in-the pole pieces.

A further modification is shown in Figs. 8 to 13 inclusive. Here again,I employ permanent magnets, as shown in Fig. 10, which are shapedsubstantially as above described. These comprise two magnet bars 60 and62 having spaced north pole ribs 63 and bottom south pole ribs 64. The

two magnets are spaced apart by a brass plate 65 and are held togetherby brass rivets 66 so that the two may be moved together as a unit. Abrass ear 61, Fig. 10, is located between the two bar magnets andsuitably secured thereto as by rivets 68 and this ear is adapted to bereciprocated by an eccentrically mounted pin 69 carried between the twohubs 10 and 1| and rotated by the handle 12, as above described.

In this particular construction, the top `work supporting plate or frame14 is made of Swedish or wrought iron and constitutes oneipole,` such asthe south pole. It has rectangular openings 15 therein within which aresecured the north -pole pieces 16 of Swedish or wrought iron, which "areheld in place by means of brass and Babbitt metal as above described.These pole pieces 16 are single members which bridge across the gapbetween the two magnets and thus contact with both of the north poleribs 63. .The cross ribs 11 between the inserts 16 extend the entiredistance between the side portions of the frame. The arrangement of themagnets and ipole pieces are otherwise as described above. The bottomplate 16 of low carbon steel is cut away to form spaced ribs 19 whichare arranged to contact with the south pole ribs of the bar magnets whenthe parts are in the position of Fig. 9. These spaced ribs 19 on thebottom plate are separated by strips of nonmagnetic material 80, such asbrass, aluminum or Babbitt metal welded or brazed into the grooves,which have their top surfaces aligned with the tops of the rib 'I9 andare so arranged that the bar magnets may slide along the surface of thebottom plate. When in the position of Fig. 13, the south poles of themagnets contact only with non-magnetic material. This constructionlikewise serves to isolate both the north and the south pole ribs of thebar magnets from the framework of the chuck and the parts forming thework supporting pole pieces. Hence, one may break the magnetic circuitat both the north and the south poles of the magnets and entirely,isolate them from the pole pieces and thus perwork plate be cut oi fromthe lines of force, and

that neither set remain in magnetic circuit with the magnet when.thework is to be removed. It', on the other hand, the work i's a roughsurfaced casting of low carbon steel or cast iron, or other metal whichdoes not readily hold residual magnetism then it is feasible to cut thelines of force issuing from either set of pole pieces, vbut leaving theother pole pieces in magnetic circuit with the magnet. A simplified formof chuck in which the permanent magnet has the spaced poles on only oneside, such as the top, is shown in Fig. 14. The permanent magnets ofhard alloy material are diicult to machine and it is, therefore,desirable to cast the magnet in substantially its nal shape and thennish by grinding only the one set of contact surfaces on one sidethereof. In such a construction, the top pole piece plate may be madethe same as shown in Figs. 1. to.13 inclusive. The bottom of thepermanent magnet 90 is not cut away but has a substantially plane facecontacting withthe south pole base plate 9| to form a permanent magneticcontact therewith irrespective of the position of the magnet. The

north pole may be formed as above described to provide ribs or polarpieces 92 spaced by grooves 93. These ribs have plane faces contactingwith the pole pieces 94 inserted in the top plate 95. This plate hasspaced cross ribs 96 forming the south pole pieces. such as Babbittmetal, spaces the inserts 94 from the ribs 96 and lies under the latterto form spaced surfaces of a sizel to receive the pole faces when-themagnets are moved to their inoperative positions. The chuck may beotherwise constructed as above described. When the magnet or magnets 90are moved laterally, the porth pole ribs 92 move into position beneaththe Babbitt metal 91 and thus the magnetic circuit is broken betweeneach rib and its pole piece 94 but the lines of force are still able topass from the south pole of the lower end of the permanent magnetthrough the iron sides of the framework to the cross ribs 96 of the topplate. Hence, these are never fully neutralized, although the 'holdingpower of the chuck is reduced sufficiently for remQval of the Work. A

These permanent magnets may require a very strong f orce for moving themlaterally and especially in a chuck of large size. If desired, I mayemploy a power mechanism for that purpose and particularly one operatedby uid pressure, such as is shown somewhat diagrammatically in Figs. 14and 15. As there shown, the magnet or magnets 90 may be attached to apiston |00 by means of a piston rod IOI. The pistonY is slidably mountedwithin a suitable piston chamber I 02 in the right hand end of theframework of thel chuck, and a screw threaded head |03 is removablymounted to form a chamber on the outside of the piston. A suitable glandand packing is provided to prevent loss of fluid around the piston androd. The piston is moved in either direction by fluid pressure from anexternal source admitted through a pipe |05 and exhausted through a pipe|06. The valve illustrated diagrammatically in Fig. 15 may comprise aslidable piston rod |01 having two valvepistons |08 and |09 suitablymounted thereon in such positions as to admit fluid underpressurethrough the ports |0 and to the opposite sides of the piston|00. The inlet pipe |05 connects with two passages opening through portsI2 and ||3 into opposite ends of thev valve chamber. The exhaust pipeconnects with the central portion of the chamber.A

Non-magnetic material 91,

The ports and the valve pistons are so spaced and larranged that whenthe handle ||5 connected to the valve stem |01 is moved towards theright, the fluid is admitted into the right hand end of the pistonchamber |02 and thus causes the permanent magnet 90 to move towards theleft or into the inoperative position indicated by the dotted lines inFig. 14. yMovement of the handle towards the left causes the magnet tobe moved to the operative position shown in Fig. 15. This powermechanism may be suitably supplied with iiuid under pressure, such ascompressed air or water or oil under hydraulic pressure. It will also beappreciated that other mechanical equivalents of the hydraulic mechanismmaybe used, such as anelectromagnet or a power operated cam or `screwmechanism. for traversing the magnet. This aspect of my invention isintended to cover such mechanical equivalents. By such arrangements, Imake it possible for one to operate and control the magnets withoutsevere vmanual exertion and make it easy to remove the work from thechuck. Y

In the chuck constructions above described, the y upper pole of eachmagnet has been of the same polarity, such as the north pole, and thetop frame has been utilized to form the south pole pieces of the worksupport. In the constructions of Figs. 16 to 20 inclusive, I have shownan ar.- rangement whereby three permanent magnets are arranged withalternately north and south poles uppermost. If desired, the set ofthree magnets may be duplicated or used in other multiple arrangement.In this construction, the inner magnet has its top of one polarity andthe tops of the two outside magnets are of the opposite polarity. Hence,the adjacent magnets form return paths for the flux from each other.This construction is such that the lines of force may permeate the polepieces readily and with greater uniformity than if only two poles ofopposite sign were employed.

As illustrated. there are three bar magnets |20, These three magnets areattached together by a non-magnetic rod |24 of brass or other suitablematerial, and they are spaced apart by brass strips |25. Each of thesepermanent magnets maybe cutaway, as shown particularly in Figs. 17 and20, so as to provide spaced ribs |26, |21, |28 and |29 at the tops andbottoms which form spaced polar faces or pieces. The

l permanent magnet |20 is located in the center -'above described of lowcarbon steel. The top |3| may be made of Swedish or wrought iron, or it'may be made of non-magnetic material, such as aluminum or brass. The topand bottom of the chuck are spaced apart by aluminum or brass sides |32or other non-magnetic material, and

, they are suitably bolted together by brass bolts |33 so as to make arigid construction. The nonmagnetic sides are preferably used because ofthe strong eld developed by this construction, and since it is desirablethat the pole pieces and associated parts of the work support beentirely cut off from both poles of the magnets when the work is to beremoved.

The lower plate |30 is cut away beneath the as from the iron bottomplate |30.

(Fig. 17). These ribs |34 are separated by noni magnetic inserts |35brazed or welded into ,the

hollows between the ribs. The ribs |34 are of the same width and lengthas the bottom south polar surfaces of the magnet |20 and they are solocated as to make proper contact with those polar sur-` faces when themagnetic lines of force are intended to pass to the work. The spacedpolar surfaces at the bottom of the central magnet |20 rest on the steelplate |30, when in an operative position, and the return circuit for theflux is through the bottom plate to each of the two outer magnets |2|and |22 which have their spaced north polar faces likewise resting onthat plate |30, as shown in Fig. 19. 'Ihese outside bar magnets |2| and|22 are likewise cut away at their bottoms the same as above describedto provide spaced north pole ribs |29. The bottom plate |30 is alsoprovided with a further set of cut out grooves similar to thoseindicated in Fig. 17 which are located beneath the bottom polar faces ofthe two outside magnets, and these cut out portions are lled with brass,aluminum or Babbitt metal |39 (Fig. 18) to form non-magnetic shoesbetween those north polar faces. That is, these non-magnetic inserts inthe bottom plate are in such an alternate arrangement that all of thebottom polar faces of the magnets make a full contact with the steelplate |30 when the magnets are in an operative position. and all ofthese polar faces contact only with the non-magnetic inserts when themagnets are moved to the inoperative position indicated in Fig. 20.

A special feature of this construction lies in the top plate and thearrangement of the -pole pieces. As indicated in Fig. 16, this top plate|3| is shaped as a hollow rectangular ring made of either mag-A netic ornon-magnetic material, but preferably Swedish or wrought iron. Thisplate is not a part of a magnetic circuit since it is isolatedmagnetically from the pole pieces carried thereby as well The top plate|3| has inserts |40 and |4| in alternate arrangement constituting thenorth and south pole pieces respectively of the work support plate. Thenorth pole pieces |40 are substantially T-shaped, as shown in Fig. 18,and their lower faces are plane and in full contact with the spacednorth polar faces of the central bar magnet |20 when the parts are in anoperative position. Similarly, the south pole pieces |4| are U-shaped,as shown in Fig. 19, and their ends' have plane faces contactf ing withthe top south polar faces of the two outer magnets when the parts are inan operative position. The pole pieces |40 and |4| may be suitably spotbrazed in position and non-magnetic material |44, such as Babbitt metal,cast into the spaces about the same so as to make a rigid work support.Brass rods |45 may be used to aid in tying the pole pieces together as arigid structure. The space beneath each end of the north pole pieces |40(Fig. 18) and the central portion of the south pole pieces (Fig. 19) isfilled with non-magnetic material of sufficient thickness to preventmaterial 'leakage of flux. The underside of the work plate has its polepieces and non-magnetic material arranged as shown in Fig. 24. In thisarrangement, the lines of force emanating' from the central bar magnet|20 will pass upwardly into the pole pieces |40 (Fig. 18) thence throughthe work and back to the pole piece of opposite polarity |4| (Fig. 19)and into the top south pole of each of the outer magnets |2| and |22 andthence to the bottom plate |30 and back to the north pole (Fig. 18) ofthe central bar magnet.

It will also be observed that the central bar magnet is substantiallytwice as wide as each of the outer magnets, so that the number of linesof force issuing from the north pole of the central magnet will beapproximately the same as the number of lines received by the adjacentsouth poles, thus providing` an even distribution of the flux andproviding a path of uniform area through the magnets. In thisarrangement of pole pieces. the flux will travel to both ends of theT-shaped north pole pieces and be distributed over the entire surface ofthe pole piece, just the same as in the flux coming from the two southpoles of the outside magnets, thus providing a satisfactory distributionof flux, as compared with the uneven distribution that would be had ifonly two magnets and L-shaped pole pieces were used.

The three bar magnets may be moved endwise from their operative toinoperative positions by a suitable construction, such as is shown inFigs. 16 and 17. This comprises a handle |41 on the end of a hub |48suitably mounted in a bearing in the aluminum side wall |32. This hubcarries an eccentric pin |49 riding in an elongated slot |50 in a lug|52 forming a part of or suitably connected to the central magnet. Theother two magnets are connected to the central magnet by the brass rods|24 and so will move therewith as the eccentric pin |49 is revolved.This serves vto move the magnets so that their polar faces contact onlywith non-magnetic material and thus isolates both poles of each magnetfrom all magnetic metal in the chuck and so cuts off the flux from thework.

For certain purposes, the construction may be as indicateddiagrammatically in Fig. 21, wherein the magnetic circuit is broken onlyat one end of each of the bar magnets, although broken at both polepieces. That is, each of the three magnets |60 has its bottom formed asa substantially plane surface contacting fully with the lower plate |62of thechuck. The top plate |64 is supported on the lower plate byaluminum or brass walls |65, as above described. The north pole pieces|66 and the south pole pieces |51 are separated by nonmagnetic material|68, the same as shown in Fig. 17, and the construction may be otherwiseas above described with reference to the construction shown in Figs. 16to 20 inclusive.

In Figs. 22 and 23, I have shown a further modification in which the topplate |10 has cross ribs forming one set of pole pieces. The plate hascut out portions |1| separated by cross ribs of iron |12. The north poleinserts |14 are suitably mounted in these cut out portions and the partsotherwise constructed as above set forth. As indicated in the dottedoutline in Fig. 23, the north pole inserts |14 correspond in shape withthe parts |40 in Fig. 18, whilethe ribs |12 are U-shaped like the ribs|4| of Fig. 19 and make proper contact with their associated spacedpolar faces |82 of the magnets |19. Non-magnetic material is located inthe under face of the top plate as above described to separate the vpolepieces and to provide for cutting off the flux.

The central magnet |18 and the two outside magnets |19 may be shaped asshown in either Fig. 20 or Fig. 21 to provide for the returnmagneticcircuit and for breaking the circuit at either the top or the bottom orat both poles of the magnets. As shown in Fig. 23, the bottom plate |84may remain in contact with all magnets, but the plate and magnets arepreferably constructed as or magnets.

shown in Fig. 20. It will be appreciated that a reverse arrangement maybe made whereby the top poles of the magnet or magnets in any of theconstructions above described may remain always in magnetic circuit withthe associated pole pieces in the work plate, and the flux broken onlyat the bottom polar faces ofthe magnet.

In'Figs. 25, 26 and 27.1 have shown an arrangement which provides forbreaking the magnetic lines of force without moving the magnet In thiscase a polar piece plate is arranged between the permanent magnet andthe top pole piece plate which supportsy the work, and the parts are soconstructed that the movable plate. may be moved to make or break themagnetic circuit. In this construction, the top plate |86 is spaced fromthe bottom plate |81 by side walls |88 of aluminum, brass or othernonmagnetic material. The permanent magnets |89 are massive bars havingflat top and bottom faces and are, therefore, easy to construct as bycasting the same and then grinding the opposite polar faces. Three ofthese magnets are employed and they are arranged the same as abovedescribed with reference to Figs. 16 to 20 inclusive. The top plate |86corresponds withl the top plate in Fig. 16 and comprises a rectangularring having the north pole pieces |90 and the south pole pieces |9|alternately arranged therein and separated by Babbitt metal |92 or othersuitable material. The north pole pieces are constructed the same as theparts |40 in' Fig. 18 and the south pole pieces the same as-the parts|4| in Fig. 19.

AThe magnetic circuit is made through a separate slidable'polar pieceplate' |94 interposed between the permanent magnets and the top workplate |86. This slide plate |94 is a rectangular member made ofnon-magnetic material, such as aluminum, brass or a Bakelite resinoid.The plate |94 is cut away to form openings within which are mounted thespaced inserts orV polar pieces |95 ,of magnetic metal, which arelocated and arranged to contact respectively with the north pole pieces|90 and the south pole pieces |9| of the work plate or to contact onlywith 'the non-magnetic material on the underside of the work plate. Theinserts or polar pieces |95 4remain in contact with their associatedmagnets and thus form spaced terminals fory the magnets'similar to theribs of the magnets shown in Figs. 3 and 10. In operation, the fluxpasses from the top of the central magnet andthe associated north polarpieces |95 of the slide plate to the lower faces of the T-shaped northpole pieces of the work plate (which are shaped like part |40 shown inFig. 18)

' and then through the work piece to the U-shaped south pole pieces (seepart |4| of Fig. 19)k of the work plate to the two south pole inserts orpolar pieces |95 of the slide plate which contact always with the twomagnets on the opposite sides arrangement, the non-magnetic portions andthe pole and polar pieces are of such dimensions and arrangement asabove indicated that the magnetic flux will not leak to the top plate toa material extent, and it may therefore be substantially completely cutoff from both the north and the south pole pieces of the work plate.This construction'makes it possible to leave the permanent magnetsalways in magnetic contact with the bottom plate of the chuck. The linesof force are cut between the north and south pole pieces wholly at thetop of the magnets and beneath the work plate.

In this arrangement, the top poles of the magnets terminate in the polarfaces at the'tops of the magnetic inserts |95. The spaced insert blocksmay be considered as movable spaced polar pieces forming a continuationof the associated magnet, so that in this construction the polar piecesare separate from the magnet and alone slide relatively to the polepieces of the work plate, whereas in the previously describedconstructions the polar pieces are formed as integral ribs on themagnets and slide therewith. A

The operation of each of the above described devices has been fully setforth. In those chucks which have a single bar magnet or a duplicationof that structure, the upper pole is in contact, or

.in direct magnetic circuit, with one set of pole pieces whilethe fluxVfrom the lower pole traverses through the side walls of the chuck tothe other set" of pole pieces. That structure which comprises threepermanent Vbar magnets or multiples thereof has 'poles arrangedalternately so of force where needed and gives a strong magnetic eld forholding the work` flrmly in position. In those chucks which have ribs orspaced polar faces at both the top and the bottom of eachmagnet,completeisolation of bothpoles of the magnet from other magnetic material of thechuck is insured so that neither the work supporting plate nor either ofits sets of pole pieces is in magnetic circuit therewith. If the spacedpolar faces are employed at only one end of the bar magnet then -theother pole thereof remains in circuit with one set of pole pieces'andwith a corresponding effect on the work. Each of these chucks has itsadvantages and fields of utility.

A primary feature lies in the use of a massive of the central magnet andform their terminal poles. The return circuit is made from one magnet toanother through the steel base plate |81 which makes a full contactwithall magnets at all times. The sliding plate |94 may be moved by anyof thev mechanisms above described to.

neutralize the work plate. As illustrated, this may comprise aneccentrically mounted pin' |98 suitably operated by a handleA and ridingin anj elongated slot in an extension |99 connected to the plate |94.

The various parts of the chuckout detrimental effect on the chuck. Manyother advantages will be inherent in these constructions as will beunderstood by one skilled in the .magnet from the other when the work isto be removed. 'I'his cuts olf the lines of force from r-one or both ofthe sets of pole pieces, and since the work supporting surface isordinarily made of metal that does not readily hold residual magnetism,then the work may be readily removed without injury to its supportingsurface or withart.

It is also to be understood that the drawings and theabove descriptionare to be interpreted as illustrative of the principles of the inventionand not as limitations thereon except as defined by `the scope of theclaims appended hereto. Many equivalent structures may be employed andAvarious modifications made in the chuck construc- Ition withoutdeparting from Athe scopel of -this invention. The pole and polar piecesmay be arranged beneath or above the magnet or in any other suitableposition, and either the magnet or the polar pieces may be moved so asto break the magnetic circuit and isolate one pole of the magnet fromthe other or from a set of the pole pieces. It will also be understoodthat the elements of non-magnetic material form non-magnetic gaps whichmay be replaced by air gaps and that the claims are to be interpreted ascovering such equivalent constructions. Numerous other modificationswill be readily apparent in view of the above disclosure.

I claim:

1. A magnetic chuck .comprising a support having a set of Amagneticallyconnected contact surfaces lying in a lower plane and separated bynon-magnetic gaps, a work plate opposed thereto having two sets ofalternately arranged, spaced, work supporting magnetic pole pieces, oneset having spaced contact surfaces in an upper plane separatedbynon-magnetic gaps, a permanent bar magnet in a magnetic circuit withsaid pole pieces and having its poles at its top and bottom respectivelywhich terminate in parts forming sets of upper and lower spaced polarfaces lying in said two planes, the distance between each two adjacentcontact surfaces in each plane being greater than the width of eachadjacent polar face, said parts being arranged for sliding the polarfaces from engagement with said contact surfaces to positions adjacentto said gaps where all of the polar faces of the magnet are isolatedfrom the pole pieces and each other, and means for sliding said partsand their polar faces relative to said contact surfaces.

2. A magnetic chuck comprising a support provided with spacedmagnetically connected contact surfaces lying in a lower plane which areseparated `by non-magnetic gaps, a work plate opposed thereto which hastwo sets of alternately arranged, spaced, work supporting magnetic polepieces, one set of the pole pieces having lower contact surfaces lyingin an upper plane which are separated by non-magnetic gaps, meansproviding a magnetic circuit between the contact surfaces of the supportand the other set of pole pieces, a permanent bar magnet having itspoles on its opposite upper andV lower sides, the top of the magnethaving spaced polar faces lying in said upper plane in engagement withsaid contact surfaces of the pole pieces, the bottom of the magnethaving spaced polar faces lying in said lower plane, the distancebetween each two adjacent contact surfaces in each plane being greaterthan the width of each adjacent polar face, said magnet being slidablymounted on the contact surfaces of the support to move' its polar facesfrom engagement with said contact surfaces to positions adjacent tothenonmagnetic gaps where they are isolated from the pole pieces, and meansfor slidably moving the magnet.

3. A magnetic chuck comprising a work plate having two sets ofalternatelyarranged, spaced, work supporting magnetic pole pieces, oneset of which has lower, spaced contact surfaces lying in an upper planeand separated by non-magnetic gaps, a lower supporting plate havingspaced magnetically connected contact surfaces lying in a plane parallelwith the upper plane and separated by non-magnetic gaps, means providinga magnetic circuit between the contact surfaces of the lower plate andthe other set of pole pieces, a permanent bar magnet having spaced,parallel ribs providing spaced polar faces on its upper and lower sideswhich lie in said planes and are arranged to contact with the adjacentcontact surfaces, the distance between each two adjacent contactsurfaces in each plane being greater than the width of each adjacentpolar face, said magnet being slidably mounted on said supporting platefor sliding said polar faces in said planes from engagement with saidcontact surfaces to positions adjacent to said gaps and vmeans forslidably moving the magnet.

4. A magnetic chuck comprising a casing, a magnetic bottom plateprovided with spaced, magnetically connected contact surfaces separatedby non-magnetic material and forming a slide surface lying in a lowerplane, a work plate having two sets of alternately arranged, spacedmagnetic pole pieces, the pieces of one set having lower contactsurfaces in an Yupper plane parallel with the lower plane, non-magneticmaterial underlying the remaining set of pole pieces and` providing aslide surface in saidplane of the lower contact surfaces of said polepieces, a member of magnetic material connecting the bottom plate withsaid remaining set of pole pieces, a permanent bar magnet slidablymounted within the casing and having spaced polar faces on its oppositetop and bottom sides lying in said planes, the distance between each twoadjacent contact surfaces in each plane being greater than the width ofeach adjacent polar face, said polar faces being slidable fromengagement with said contact surfaces into contact with the non-mag,-netic material of the two plates and means for sliding the magnet tosaid positions to make or break the magnetic circuit between the polepieces and both poles of themagnet.

5. A magnetic chuck comprising a work plate providing two sets ofalternately arranged, spaced, work supporting magnetic pole pieces, thepieces of one set having spaced contact surfaces o n their under sideslying in a single upper plane and separated by non-magnetic gaps, asupport having a set of spaced magnetically connected contact surfaceslying in a single lower plane and separated by non-magnetic gaps, aplurality of separated, permanent bar magnets in magnetic circuit withsaid pole pieces which have their poles at their tops and bottomsrespectively 'terminating in parts forming upper and lower spaced polarfaces lying in said planes and slidably contacting magnetically withsaid contact surfaces, the distance between each two adjacent contact,surfaces in each plane being greater than the width of each adjacentpolar face, the parts forming said polar faces being slidable as a unitto move said polar faces in said planes and position them in contactwith said contact surfaces or alternatively adjacent to said gaps wherethey are isolated from the work plate and support, and means for causingsuch sliding movement.

6. A magnetic chuck comprising a lower magnetic plate having contactsurfaces lying in a single lower plane which are separated bynonmagnetic gaps, a wcrk plate having alternately arranged, spaced, worksupporting magnetic pole pieces providing lower contact surfaces in asingle upper plane and separated by non-magto said non-magnetic gapswhere the magnets are isolated from each other and all of said polepieces, and means for thus sliding the magnets.

'1. A magnetic chuck comprisingy a bottom plate having spaced butmagnetically connected contact surfaces in a lower plane alternatingwith spaced non-magnetic surface portions, a work plate having two setsof alternately arranged, spaced magnetic pole pieces, spacednon-magnetic material underlying one set of pole pieces, the other setof pole pieces providing lower contact surfaces'in an upper planeparallel with the lower plane, a plurality of movable permanent barmagnets, each having a set of ribs on the upper and lower sidesproviding spaced polar faces at each of its opposite poles, the distancelbetween each two adjacent contact surfaces in each plane being greaterthan the width of each adjacent vpolar face, the sets of polar facesbeing 4respectively arranged in said planes to contact magnetically withsaid. lower contact surfaces of the pole pieces and the magneticportions of the bottom plate in a first position or alternatively in asecond position to contact with said non-magnetic portions and material,and means for moving said' magnets from the rst to the second positionto locate their polar faces adjacent to the non-magneticportions andmaterial and thereby isolate all ofthe magnet poles from all ofl the'pole pieces of the work plate.

8. A magnetic chuck comprising a casing having a lower magneticsupporting member, a work plate having two sets of alternatelyarranged-spaced magnetic pole pieces, each set having lower contactsurfaces in a single plane which are separated by non-magnetic gaps,nonmagnetic material'which isolates said member from the work plate, aplurality of permanent bar magnets in the casing mounted on v saidmember and having their poles at their tops and bottoms in analternating reverse polar arfaces in each plane being greater than theWidth non-magnetic gaps, a plurality of permanent bar magnetshavingupper and lower poles in an alternate reverse p'olar arrangement, eachmagnet having parts forming spaced polar faces at each of its poleswhich lie in said planes, the distance between each two adjacent contactsurfaces in each plane being greater than the width of each adjacentpolar face, means which mag-V netically isolates the two plates so thatone mag- `net forms a return path for the flux of another,

. having two sets of alternately arranged, spaced rangement, the upperVpoles terminating in parts forming sets of spaced nat polar faces ofopposite polarity which are slidable in said plane and operativelycontact magnetically with the contact surfaces 'of both sets of saidpole pieces, the

faces being greater than the width of each adjacent polar face, thelower poles of the magnets contacting magnetically with said member,

and means whereby said parts may be moved to slide the polar faces insaid plane from engage-v set having lower contact surfaces lying in avsingle upper plane and separated by non-mag- 'netic gaps, a supportingplate having magnetically connected portions providing contact surfacesin a lower plane which are separated by distance between eachtwoadjacent contact surmagnetic pole pieces having exposed lower contactsurfaces in a single upper plane which are separated by non-magneticmaterial, a bottom plate having magnetically connected material.providing spaced contact surfaces in a lower tacting magnetically withsaid contact surfaces, f the distance between each two adjacent contactsurfaces in each plane `being greater than the 4width of each adjacentpolar face, the polar` faces, contact surfaces and non-magnetic materialbeing arranged so that the polar faces may be moved in parallel planesto contact solely with said magnetic material or alternatively to beisolated from each other and the pole pieces by contacting only withsaid non-magnetic material, and means for sliding the magnets to form amagnetic circuit with a work piece or to break the circuit.

11. A magnetic chuck comprising a work plate having two sets ofalternately arranged, spaced magnetic pole pieces, each piece of one setbeing T-shaped and having a depending contact arm, each piece of theother set being U-shaped and having two spaced depending contact arms,the arms of each set having lower contact faces in aplane, meansproviding non-magnetic gaps between said contact arms, three movablepermanent bar magnets of reverse polarity arrangement, each having parts`forming top and bottom spaced polar faces in upper 'and lower parallelplanes, the upper polar faces of one magnet contacting operatively withthe contact surfaces of the arms of the T-shaped pole pieces,

and the upper polar faces of the other two magnets `contactingoperatively with the contactasurfaces of the arms of the U-shaped polepieces. a bottom plate having spaced contact surfaces lying in saidlower planeand separated by nonmagnetic gaps, the distance between eachtwo adjacent contact surfaces in each plane being greater than the widthof each adjacent polar face, the magnets being slidably mounted so thatthe polar faces may be moved from engagement with said surfaces and beisolated by said gaps,- and means for slidably moving the magnets.

FRANK L. SIMMONS.

